This invention relates generally to railyard management, and more particularly to a yard performance model for expediting and simplifying the process of moving railcars through a railyard from arrival to departure.
A terminal area is primarily used to reorganize incoming freight into new trains, which then move the freight to further destinations. A terminal area comprises one or more switchyards and interconnecting rails, and the performance of the entire terminal area depends primarily on the activities within the terminal switchyard(s) and the efficient dispatch of traffic within the terminal area. Thus, a terminal area in effect can be visualized as a small railroad network in and of itself, with the primary activities of managing the dispatch of traffic within the terminal area, and building trains within the switchyard(s).
Railroad resources and activities are often analyzed hierarchically, from a network, regional, and local perspective. The regional perspective primarily emphasizes the intra-regional flow of traffic between terminal areas within a region, with the primary purpose of assuring that trains meet their schedules. As such, the regional perspective of the terminal area is not concerned with the details of train building in the terminal area, but with the overall ability of the terminals to meet the schedule for the flow of trains into and out of the terminal area.
Rail corridors and terminals present an alternating sequence of services to railcars. The services alternate between transportation and routing. These services and the resources required are in limited supply. The objective of the regional level of network planning is to allocate the available resources and services within a given time period to optimize the flow of a collection of trains. This requires optimizing over time the allocation of a very large collection of factors, such as, rail segments, switches, crews, locomotives, yard personnel, and yard facilities. Such an optimization is computationally infeasible. However, the regional view of yards and corridors is feasible using modeling techniques, which provide accurate, but not necessarily perfect, views of the capacities of yards and corridors and the relevant services involved in moving trains through the system.
The train building process in a switchyard requires the use of tightly coupled and limited resources, with difficult constraints to be met as to train arrival and departure schedules. To model the process in detail, including the order of all operations, requires extensive mathematical development, and is dependent on yard topology. Therefore, it would be desirable to provide a method of allocating the available resources and services within a railyard in a given time period to optimize the flow of a collection of trains.
The regional concept of the switchyard provides a simplified switchyard model posed as a sequence of car flows between reservoirs, representing the sequence of tasks performed on each car during the (TBP), with each reservoir having a limited capacity, and the flows between reservoirs being dynamically modulated over time by various factors present in every yard.